<ul>
<li>The second exam will be tomorrow, starting at 8:45am in SHS 126;</li>
<li>A revised cheat sheet is now available. Comments are always welcome;</li>
<li>The solutions for the last homework are up, although as of 4:00pm problem 1 was not complete.</li>
</ul>

Sometimes we consider the wieght of blocks (-mgj) and sometimes we don’t to find eqns of motion. How can you tell when you are or are not supposed to include gravity force??? Also, in one of his problems (Spring “03” exam 1 Problems 2 & 5) in one of the steps a new coordinate is defined measuring the displacement of the system from static equil. Does anyone know when/ why/ how to use this??

> For a problem like the last homework the quarter car, is the solution
> always the same x(t) = exp(-zeta*wn*t) (Acos(wd*t)+ Bsin(wd*t)) and
> then solve the A and B from inition conditions, and wd changes with the
> value of zeta?
>
> I see on the cheat sheet it has different formulations of zeta, but I
> can’t seem to get how the general equations are set up unless this is
> general for all of them. If you can help shed any light on this (I
> don’t need you to reteach me everything), I just don’t understand w/out
> doing the dq every time where someone has general equations for if
> we’re given in like Problem 4 of Homework 4 where we know meq beq keq
> what form... thanks